Industrial plants working with bulk materials require uniform quality of the materials supplied in the interest of continuous and optimum operation. This task is simplified by keeping the differences in the composition of basic materials as small as possible. The raw materials supplied are not merely used in the states in which they are supplied, but rather are subjected to a previous process of blending and unifying. Suitably, this equalization is done in connection with bunkering for storage.
Piles of staple materials are known to be a very favorable method of bunkering for ores with respect to investment costs. It is also successfully used for anthracite, lignite, and other bulk materials when dealing with large quantities of material. In order to utilize a staple pile while at the same time insuring constant quality of the raw materials thus stacked, the staples must be accumulated in a certain fashion, and especially, withdrawn or broken down in a certain fashion.
The basic idea is to distribute the flow of material supplied by a conveyor installation over the entire length of the pile in such a manner that any pile cross section contains a small quantity representative of all types of material used to build up the pile. If a thin slice extending over the cross section of the pile is taken, the contents of such slice would be made up of a mixture of small quantities of all types of material supplied, and it represents an average quality of the materials used to form the pile.
The magazine LIGNITE, Issue 2, Feb. 1966, pages 47 to 51, discusses a blade pick-up pipe or tube consisting of one pipe whose outer circumference is fitted with offset blades, and of a two-piece raking device covering the frontal slope of the pile to feed the pipe. The bladed pipe extends the entire breadth of the foot of the pile, and revolves at a constant speed. The bipartite rake moves back and forth in countermovement. The material mixture thus collecting at the foot of the pile is picked up by the blades of the bladed pipe or tube, and is brought to a conveyor belt arranged in the interior of the bladed pipe.
It is the object of the present invention to improve upon the known apparatus, particularly to achieve a more complete and consistant charging of the removal belt combined with an increase in the mixing effect when receiving the goods, whereby the construction and function of the apparatus remains as simple as possible. To solve this problem, the invention includes four pick-up spirals of blades distributed evenly over the circumference of the pick-up pipe, with each spiral having two blades arranged parallel with the front of the pile, and each with an embracing angle of 270.degree.. Also, the velocity ratio between removal belt velocity and the rate of advance of the delivery points of the blades on the spirals is 0.6. In a mixing bed pile apparatus with pipe blade pick-up where such conditions are maintained, maximum results are obtained with respect to charging of the belt and the mixing ratio.
The pile mixing bed apparatus of the invention has, furthermore, an advantage over known apparatus in that the number of blades has been reduced considerably, thus facilitating a more shallow incline of the blade helix around the pipe. The reduction in the blade number entails considerable advantages when reversing operation, because a reduced number of blades has to be tilted or adjusted, which results in a time saving. The invention, therefore, represents a simplification coupled with greater economy, and the simultaneous ideal charging of the removal belt in connection with better mixing effect on account of the ratio between pipe revolution, spiral incline and belt velocity.
The following description illustrates an example of the arrangement and performance of a bladed pipe pick-up with the pipe or tube separated into 24 sections of even length, each of which corresponds to the length of a blade. Each section is complete with four blades evenly distributed over the circumference, such blades being regularly offset from section to section in such a manner that they form four cascade spirals according to the invention, with an embracing angle of 270.degree.. To illustrate the charging of the belt, the belt has been divided into sections of even length, which are in integral relation to the blade length and/or bladed pipe section length. The following illustrated example is based on a belt section length of one fifth of the blade length.